Auto focus and optical image stabilization in a compact folded camera

ABSTRACT

Compact folded camera modules having auto-focus (AF) and optical image stabilization (OIS) capabilities and multi-aperture cameras including such modules. In an embodiment, a folded camera module includes an optical path folding element (OPFE) for folding light from a first optical path with a first optical axis to a second optical path with a second optical axis perpendicular to the first optical axis, an image sensor and a lens module carrying a lens with a symmetry axis parallel to the second optical axis. The lens module can be actuated to move in first and second orthogonal directions in a plane perpendicular to the first optical axis, the movement in the first direction being for auto-focus and the movement in the second direction being for OIS. The OPFE can be actuated to tilt for OIS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application from U.S. patentapplication Ser. No. 16/289,672 filed Mar. 1, 2019 (now allowed), whichwas a continuation application from U.S. patent application Ser. No.15/917,701 filed Mar. 11, 2018 (now allowed), which was a continuationapplication from U.S. patent application Ser. No. 15/303,863 filed Oct.13, 2016 (now U.S. Pat. No. 9,927,600), which was a 371 application frominternational patent application PCT/IB2016/052179 filed Apr. 15, 2016,and is related to and claims priority from U.S. Provisional PatentApplications No. 62/148,435 filed on Apr. 16, 2015 and No. 62/238,890filed Oct. 8, 2015, both applications expressly incorporated herein byreference in their entirety.

FIELD

Embodiments disclosed herein relate in general to digital cameras and inparticular to folded-lens digital cameras and dual-aperture digitalcameras with a folded lens.

BACKGROUND

In recent years, mobile devices such as cell-phones (and in particularsmart-phones), tablets and laptops have become ubiquitous. Many of thesedevices include one or two compact cameras including, for example, amain rear-facing camera (i.e. a camera on the back face of the device,facing away from the user and often used for casual photography), and asecondary front-facing camera (i.e. a camera located on the front faceof the device and often used for video conferencing).

Although relatively compact in nature, the design of most of thesecameras is similar to the traditional structure of a digital stillcamera, i.e. it comprises a lens module (or a train of several opticalelements) placed on top of an image sensor. The lens module refracts theincoming light rays and bends them to create an image of a scene on thesensor. The dimensions of these cameras are largely determined by thesize of the sensor and by the height of the optics. These are usuallytied together through the focal length (“f”) of the lens and its fieldof view (FOV)—a lens that has to image a certain FOV on a sensor of acertain size has a specific focal length. Keeping the FOV constant, thelarger the sensor dimensions (e.g. in a X-Y plane), the larger the focallength and the optics height.

In recent times, a “folded camera module” structure has been suggestedto reduce the height of a compact camera. In the folded camera modulestructure, an optical path folding element (referred to hereinafter as“OPFE”) e.g. a prism or a mirror (otherwise referred to hereincollectively as a “reflecting element”) is added in order to tilt thelight propagation direction from perpendicular to the smart-phone backsurface to parallel to the smart-phone back surface. If the foldedcamera module is part of a dual-aperture camera, this provides a foldedoptical path through one lens module (e.g. a Tele lens). Such a camerais referred to herein as a “folded-lens dual-aperture camera” or a“dual-aperture camera with a folded lens”. In general, the folded cameramodule may be included in a multi-aperture camera, e.g. together withtwo “non-folded” camera modules in a triple-aperture camera.

In addition to the lens module and sensor, modern cameras usuallyfurther include a mechanical motion (actuation) mechanism for two mainpurposes: focusing of the image on the sensor, and optical imagestabilization (OIS). For focusing, in more advanced cameras, theposition of the lens module (or at least of a lens element in the lensmodule) can be changed by means of an actuator and the focus distancecan be changed in accordance with the captured object or scene.

The trend in digital still cameras is to increase the zoomingcapabilities (e.g. to 5×, 10× or more) and, in cell-phone (andparticularly smart-phone) cameras, to decrease the sensor pixel size andto increase the pixel count. These trends result in greater sensitivityto camera shake for two reasons: 1) greater resolution, and 2) longerexposure time due to smaller sensor pixels. An OIS mechanism is requiredto mitigate this effect.

In OIS-enabled cameras, the lens module lateral position can be moved,or the entire camera module can be tilted in a fast manner to cancelcamera shake during-image capture. Camera shakes shift the camera modulein 6 degrees of freedom, namely linear movements in X-Y-Z, roll (“tiltabout” or “tilt around”) the X axis, yaw (tilt around the Z axis) andpitch (tilt around the Y axis). While the linear motion in X-Y-Znegligibly affects the image quality and does not have to becompensated, compensation of the tilt angles is required. OIS systemsshown in known designs (see e.g. US 20140327965A1) correct yaw andpitch, but not roll motion.

A folded-lens dual-aperture camera with an auto-focus (AF) mechanism isdisclosed in Applicant's US published patent application US 20160044247,the description and figures of which are incorporated herein byreference in their entirety.

SUMMARY

FIG. 1 shows a schematic illustration of a design that provides a “lowheight” folded camera module. The figure shows a folded camera module100 comprising an OPFE 102, a lens module 104 configured to mechanicallyhold lens elements therein, and an image sensor 106.

OPFE 102 can be for example any one of a mirror, a prism or a prismcovered with a metallic reflecting surface. OPFE 102 can be made ofvarious materials including for example plastic, glass, a reflectivemetal or a combination of two or more of these materials. According tosome non-limiting examples, the lens module in camera 100 has a 6-15 mmfocal length (“Tele lens”), and it can be fitted in a dual-aperturecamera together with a second non-folded camera module having a 3-5 mmfocal length (“Wide lens”) lens and a second sensor (not shown).

AF functionality for the Tele lens is achieved by moving the lens module104 along the Z axis. The Applicant has found that OIS functionality forcamera 100 can be achieved in at least two ways. To compensate forcamera tilt around the Z axis, lens module 104 can be shifted in the Ydirection and/or OPFE 102 can be tilted around the Z axis or the X axis.However, optical analysis performed by the Applicant has shown that thetilt of the OPFE around the Z axis introduces also an undesired tilt ofthe image around the Z axis (roll) on sensor 106. This solution is thuslacking, since it contradicts the basic idea behind OIS functionalityand since it also increases computational fusion time (needed forgenerating a fused image in a dual aperture camera from fusion of theWide image, generated by the Wide lens, and a Tele image, generated bythe Tele lens) due to image disparity of the Tele and Wide sensors.

Applicant has further found that to compensate for camera tilt aroundthe Y axis, the lens module can be moved in the X direction and/or theOPFE can be tilted around the Y axis. However, it has also been found bythe Applicant that when shifting the lens module in the X direction, theheight of the module will increase. Shifting the lens module in the Xdirection for OIS and in the Z direction for focus may require toincrease module height to about 9-9.5 mm for a lens with a diameter of6-6.5 mm, as is the case with known OIS solutions. This height additionreflects directly on the phone thickness and is undesirable inaccordance with modern smart-phone design requirements.

Accordingly, the presently disclosed subject matter includes a foldedcamera module comprising both AF and OIS mechanisms in a manner allowingmaintenance of a desired folded camera module height. Furthermore, theincorporation of such mechanisms and capabilities does not result incompromising camera height. The presently disclosed subject matterfurther contemplates a folded-lens dual-aperture camera thatincorporates such a folded camera module.

Embodiments disclosed herein teach folded camera modules and folded-lensdual-aperture cameras in which the OIS functionality is divided betweentwo optical elements as follows: a shift of the folded lens module alongone axis (e.g. the Y axis) and rotation of the OPFE about an axisparallel to the same axis.

In an embodiment, there is provided a folded camera module comprising anOPFE for folding light from a first optical path to a second opticalpath, the second path being along a second optical axis. The foldedcamera module further comprises an image sensor, and a lens modulecarrying a lens assembly with a symmetry axis along the second opticalaxis, wherein the lens module is designed to move in a first directionand in a second direction orthogonal to the first direction, the firstand second directions being in a plane containing the second opticalaxis and perpendicular to a plane containing the first and secondoptical paths, and wherein the OPFE is designed to be tilted around thesecond direction.

Note that as used herein, “tilt around a direction” means tilt around aline or axis in, or parallel to, the direction.

In an embodiment, the lens module movement is in the first directionalong the second optical axis for AF and the lens module movement in thesecond direction orthogonal to the first direction is for OIS,compensating for tilt of the camera module around the first direction.

In an embodiment, the OPFE movement is for OIS, compensating for tilt ofthe camera module around the second direction.

In an embodiment, a folded camera module further comprises a lensactuation sub-assembly configured to cause-lens module movement in thefirst and second directions, and an OPFE actuation sub-assemblyconfigured to cause movement of the OPFE so as to tilt the first opticalpath.

In an embodiment, each of the lens actuation and OPFE actuationsub-assemblies includes a plurality of flexible hanging members.

In an embodiment, the flexible hanging members of the lens actuationsub-assembly are parallel to each other.

In an embodiment, the flexible hanging members of the OPFE actuationsub-assembly are tilted.

In an embodiment, a folded camera module further comprises an actuationcontroller configured to receive data input indicative of tilt in atleast one direction and data input from position sensors coupled to thelens actuation sub-assembly, and, responsive to the data inputs,configured to generate instructions to the lens actuation sub-assemblyto cause movement in the second direction for optical imagestabilization (OIS).

In an embodiment, the actuation controller is further configured toreceive data input indicative of tilt in at least one direction and datainput from position sensors coupled to the OPFE actuation sub-assembly,and, responsive to the data input, configured to generate instructionsto the OPFE actuation sub-assembly to cause movement of the OPFE forOIS.

In an embodiment, the actuation controller is further configured toreceive data input indicative of focus, and, responsive to the datainput, configured to generate instructions to the lens actuationsub-assembly to cause movement in the first direction for AF.

In an embodiment, the OPFE movement to tilt is around an axisperpendicular to the first and second optical directions.

In an embodiment, the lens module movement in the first direction isparallel to the second optical axis and the lens module movement in thesecond direction is perpendicular to the second optical axis.

In an embodiment, the OPFE includes a prism.

In an embodiment, the OPFE includes a mirror.

In an embodiment, the lens actuation sub-assembly includes a pluralityof coil-magnet pairs for actuating the lens module movement in the firstand second directions.

In an embodiment, the plurality of coil-magnet pairs includes twocoil-magnet pairs.

In an embodiment, the plurality of coil-magnet pairs includes threecoil-magnet pairs.

In an embodiment, the plurality of coil-magnet pairs includes fourcoil-magnet pairs.

In an embodiment, one of the four coil-magnet pairs is positionedbetween the lens module and the image sensor.

In an embodiment, a camera module further comprises one or more positionsensors associated with a coil-magnet pair, the one or more positionsensors enabling measurement of a position of the lens module.

In an embodiment, the one or more position sensors enable positionmeasurement of the lens module along the first and second movementdirections.

In an embodiment, the one or more position sensors further enablesposition measurement of the lens module in a tilt around an axisperpendicular to the first and second movement directions.

In an embodiment, a position sensor is coupled to the lens actuationsub-assembly and to the actuation controller such as to allow movementof the lens module along the first and second movement directions whilepreventing tilt around an axis perpendicular to the first and secondmovement directions.

In an embodiment, the one or more position sensors include a Hall-barsensor.

In an embodiment, two or three coil-magnet pairs are arranged topassively prevent undesired tilt around an axis that lies in the planecontaining the first and second optical paths and is perpendicular tothe second optical axis.

In an embodiment, three coil-magnet pairs are arranged to activelyprevent undesired tilt around an axis that lies in the plane containingthe first and second optical paths and is perpendicular to the secondoptical axis.

In an embodiment, there is provided a dual-aperture camera, comprising afolded camera module of any embodiment above and a non-folded cameramodule comprising a non-folded camera image sensor and a non-foldedcamera lens module with a lens axis along a first optical axisperpendicular to the second optical axis.

The presently disclosed subject matter further contemplates amulti-aperture camera, comprising three or more camera modules, where atleast one of the camera modules is a folded camera module as describedabove and any one of the other camera modules can be either a foldedcamera module or a non-folded camera module.

The presently disclosed subject matter further includes a method ofcompensating for tilt in a folded camera module comprising an OPFE, alens module carrying a lens assembly and an image sensor, the methodcomprising: using the OPFE for folding light from a first optical pathto a second optical path, the second optical path being along a secondoptical axis, the lens module having a symmetry axis along the secondoptical axis, moving the lens module in a first direction and in asecond direction orthogonal to the first direction, the first and seconddirections being in a plane containing the second optical axis andperpendicular to a plane containing the first and second optical paths,wherein the lens module movement in the first direction is for autofocusand the lens module movement in the second direction orthogonal to thefirst direction is for OIS, compensating for tilt of the camera modulearound the first direction, and moving the OPFE to be tilted around thesecond direction, wherein the OPFE movement is for OIS, compensating fortilt of the camera module around the second direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of embodiments disclosed herein are describedbelow with reference to figures attached hereto that are listedfollowing this paragraph. The drawings and descriptions are meant toilluminate and clarify embodiments disclosed herein, and should not beconsidered limiting in any way. Like elements in different drawings maybe indicated by like numerals. Elements in the drawings are notnecessarily drawn to scale.

FIG. 1 shows a schematic illustration of a folded camera modulecomprising both AF and OIS mechanisms, according to an example of thepresently disclosed subject matter;

FIG. 2A shows schematically an isometric view of a folded camera modulecomprising both AF and OIS mechanisms, according to an example of thepresently disclosed subject matter;

FIG. 2B shows schematically a functional block diagram of a deviceincluding a folded camera module operative to perform AF and OIS,according to an example of the presently disclosed subject matter;

FIG. 3A shows schematically an isometric view of a dual-aperture camerathat includes the folded camera module of FIG. 2 together with a second,upright camera module, according to an example of the presentlydisclosed subject matter;

FIG. 3B shows schematically an external view of a dual-aperture camerathat includes the folded camera module of FIG. 2 together with a second,upright camera module, according to an example of the presentlydisclosed subject matter;

FIG. 4 shows schematically an isometric view of the dual-aperture cameraof FIG. 3A with the folded lens module removed from its mounting andturned upside down, according to an example of the presently disclosedsubject matter;

FIG. 5A shows an exploded isometric view of an embodiment of an OPFEactuation sub-assembly, in which the OPFE in the form of a prism,according to an example of the presently disclosed subject matter;

FIG. 5B shows a side view of part of the OPFE actuation sub-assembly ofFIG. 5A, according to an example of the presently disclosed subjectmatter;

FIG. 5C shows an isometric exploded view of an OPFE actuationsub-assembly, in which the OPFE is in the form of a mirror, according toan example of the presently disclosed subject matter;

FIG. 5D shows a side view of part of the OPFE actuation sub-assembly ofFIG. 5C, according to an example of the presently disclosed subjectmatter;

FIG. 5E shows schematically the AF and OIS movements of the lens moduleand the OIS tilt movement of the OPFE, according to an example of thepresently disclosed subject matter;

FIG. 6 shows various views of another embodiment of an OPFE actuationsub-assembly, in which the OPFE is in the form of a prism, according toan example of the presently disclosed subject matter: (a) isometricview, (b) external side view, (c) internal side view and (d) bottomisometric view;

FIG. 7 shows details of an actuator in a folded camera module disclosedherein, according to an example of the presently disclosed subjectmatter;

FIG. 8 shows the actuator of FIG. 7 along a cut A-A shown in FIG. 7 inan isometric view;

FIG. 9A shows the actuator of FIG. 7 along a cut A-A shown in FIG. 7 ina side view;

FIG. 9B shows a magnetic simulation along the same cut A-A, where thearrows show the magnetic field direction, according to an example of thepresently disclosed subject matter;

FIG. 10 shows an arrangement for lens actuation with three actuators,according to an example of the presently disclosed subject matter;

FIG. 11 shows an arrangement for lens actuation with two actuators,according to an example of the presently disclosed subject matter.

FIG. 12A shows schematically an isometric view of another folded cameramodule comprising both AF and OIS mechanisms, according to an example ofthe presently disclosed subject matter;

FIG. 12B shows schematically an isometric view of the dual-aperturecamera of FIG. 12A with the folded lens module removed from itsmounting, according to an example of the presently disclosed subjectmatter;

FIG. 12C shows schematically an isometric view of the dual-aperturecamera of FIG. 12A with the folded lens module in (a) a regular view and(b) turned upside down, according to an example of the presentlydisclosed subject matter; and

FIG. 13 shows schematically a magnet in the folded lens module of FIG.12C coated with an absorption and scattering coating, according to anexample of the presently disclosed subject matter.

DETAILED DESCRIPTION

In the description below (and as shown at least in FIG. 2) a reflectingelement (OPFE) 208 reflects light from a first optical path or direction205 to a second optical path or direction 206 (the latter convergingwith the second optical axis). Both the first and second opticaldirections define a plane (herein “first plane”) that contains bothoptical axes.

The following system of orthogonal X-Y-Z coordinates is chosen by way ofexample and for explanation purposes only: the Z axis is parallel to (orcoaxial with) the second optical axis, the second optical axis being anaxis of the folded camera module described below; the Y axis isorthogonal to a first optical axis and to the second optical axis; theX-axis is orthogonal to the Y and Z axes.

FIG. 2A shows schematically an isometric view of a folded camera modulenumbered 200, according to an example of the presently disclosed subjectmatter. Folded camera module 200 comprises an image sensor 202 having animaging surface in the X-Y plane, a lens module 204 with an optical axis206 defined above as “second optical axis” and an OPFE 208 having asurface plane 210 tilted to the image sensor surface, such that lightarriving along a first optical path or direction 205 is tilted by theOPFE to the second optical axis or direction 206.

Folded camera module 200 further comprises a lens actuation sub-assembly230 (shown in FIG. 4) for moving lens module 204 in the Y-Z plane(“second plane”). Lens actuation sub-assembly 230 comprises a lensbarrel 214 (made for example from plastic), which houses lens elements204. Lens actuation sub-assembly 230 further comprises a hangingstructure comprising four flexible hanging members 216 a-d that hanglens barrel 214 over a base 218 (see FIG. 4). Members 216 a-d areparallel to each other. In some embodiments, members 216 a-d may be inthe form of four wires and may be referred to as “wire springs” or“poles”. Hanging members 216 a-d allow in-plane motion which is known inthe art and described for example in Applicant's published PCT patentapplication No. WO2015/068056, the description and figures of which areincorporated herein by reference in their entirety. The hangingstructure with members 216 a-d thus allows a first type of motion of thelens module relative to the base in substantially the Y-Z plane underactuation by three actuators.

An actuator can be for example of a type sometimes referred in the artas “voice coil motor” (VCM). Lens actuation sub-assembly 230 furthercomprises three magnets 222 a-c (shown in FIG. 4) that are part of threemagnetic structures (e.g. VCMs) referred to hereafter as first actuator,second actuator and third actuator, respectively. Each actuatorcomprises a coil in addition to a respective magnet. Thus, the firstactuator comprises magnet 222 a and a coil 224 a, the second actuatorcomprises magnet 222 b and a coil 224 b and the third actuator comprisesmagnet 222 c and a coil 224 c.

Camera module 200 further comprises an OPFE actuation sub-assembly thatallows tilting of OPFE 208. A first embodiment numbered 260 of such anactuation sub-assembly is shown in FIGS. 5A-E.

FIG. 2B shows schematically a functional block diagram of device 250that includes a folded camera module such as module 200, operative toperform AF and OIS. The device can be for example a portable electronicdevice such as a smart-phone. Device 250 includes, in addition to foldedcamera module 200, a gyroscope 262, an OIS/AF actuationdriver/controller 264 (also referred to simply as “actuationcontroller”) and a portable device/phone controller 266. The foldedcamera module is shown including elements described above and below. Theperformance of OIS and AF by device (e.g. a smart-phone) 250 isdescribed in detail below. In general, gyroscope 262 provides data inputindicative of tilt in at least one direction to controller 264.Similarly, position sensors 226 a-c and 246 (the latter described below)are configured to provide position inputs to driver/controller 264.Device/phone controller 266 is coupled to the image sensor and isconfigured to provide instructions to actuation controller 264. Theinstructions include, for example, AF desired position and/or OIS toggleon/off. Actuation controller 264 can provide actuation commands,responsive to the data input from gyroscope and position sensors, toactuation coils 224 a-c and 244 (the latter described below) forgenerating motion compensating for the detected tilt and/or forobtaining a desired focus position.

Folded camera module 200 can for example be included in a folded-lensdual-aperture camera described in Applicant's US published patentapplication US 20160044247. FIG. 3A shows schematically an isometricview of a folded-lens dual-aperture camera 300 that includes the foldedcamera module of FIG. 2 together with a second, upright camera module.FIG. 3B shows schematically camera 300 in an external view. Camera 300includes, in addition to folded camera module 200, an upright(non-folded) camera module 280 having a first optical axis 252 which isperpendicular to the second optical axis and to the second plane. Theheight of the dual-aperture camera is indicated by H. H can be forexample between 4 mm-7 mm.

FIG. 4 shows, for clarity, camera 300 including folded camera module 200with lens actuation sub-assembly 230 (comprising lens barrel 214 and itspoles 216 a-d) disassembled from base 218 and turned upside down,showing an underside with two plate sections 220 a and 220 b. The threemagnets 222 a-c are positioned (e.g. rigidly assembled/mounted/glued) onthe underside plate sections.

The three corresponding coils 224 a-c are positioned on base 218. Whenlens actuation sub-assembly 230 is assembled, magnets 222 a, 222 b and222 c are located just above coils 224 a, 224 b and 224 c, respectively.As described below (“magnetic operation” section), in operation, aLorentz force may be applied on coil 224 a along the Y axis directionand on two magnets 222 b-c along the Z axis direction. As furtherdescribed below (“mechanical operation” section), having these threeforces on the three magnets allows three mechanical degrees of freedomin the motion of the center of mass of lens actuation sub-assembly 230:linear Y and Z motions, and tilt around X axis motion.

The motion of the lens actuation sub-assembly 230 in the Y and Zdirections (i.e. in the Y-Z plane) can be measured by position sensors,for example Hall-bar sensors (or just “Hall-bars”) 226 a-c which arecoupled to the magnetic field created by, respectively, magnets 222 a-c.When the lens module moves in the Y-Z plane, the magnetic field sensedby Hall-bars 226 a-c changes and the motion can be sensed at threepoints, as known in the art. This allows determination of three types ofmotion, i.e. Y direction motion, Z direction motion and tilt around Xaxis motion.

FIG. 5A shows an exploded isometric view of OPFE actuation sub-assembly260, according to an example of the presently disclosed subject matter.According to the illustrated example, OPFE actuation sub-assembly 260includes hinge springs 236 a-b that suspend the prism and which canconvert linear to angular motion. These hinge springs allow tilting ofprism 208 around a hinge axis 232, which is parallel to, or along the Yaxis. The tilt can be for example ±1° from a zero (rest) position of theprism.

In an embodiment shown in FIG. 5A, the hinge springs may be in the formof single-part flexible supports 236 a and 236 b, each attached at aside of the prism. The prism and its reflecting surface plane 210, hingeaxis 232 and flexible support 236 b are also shown in a side view inFIG. 5B. Actuation sub-assembly 260 further includes an actuator 238(referred to hereinafter as a “fourth” actuator) that includes a magnet242 rigidly coupled to prism 208 (in the illustrated example—through anadaptor 215) and a coil 244 rigidly coupled to a base 212′.

Regarding a hinge spring, it can be designed in at least two differentways. In one design, mentioned and shown in FIGS. 5A and 5B, the hingespring may comprise two single-part flexible supports 236 a and 236 battached at each side of the prism. Another design is illustrated inFIGS. 5C and 5D. FIG. 5C shows an isometric exploded view of anotherembodiment of an OPFE, actuation sub-assembly 260′, in which the OPFE isin the form of a mirror 208. FIG. 5D shows actuation sub-assembly 260′assembled, in a side view. Actuation sub-assembly 260′ includes a hingespring having two sets of leaf springs mounted at each side of themirror, a first set having two spring members 240 a and 240 bperpendicular to each other and a second set having two spring members240 c and 240 d perpendicular to each other. The rotation axis will bearound a virtual line drawn between the intersection points of eachsprings set 240 a-b and 240 c-d. FIG. 5E shows schematically the AF andOIS movements of the lens module and the OIS tilt movement of the OPFE.

The hinge spring of any of the embodiments presented may convert forcein any direction parallel to the X-Z plane to a torque around the Y axissuch that tilt around the Y axis is created.

As described with reference to FIGS. 5C and 5D and further below, inoperation, a Lorentz force may be applied between coil 244 and magnet242 in order to move magnet 242 in a direction indicated by an arrow 254(FIG. 5D). This force (and magnet movement) is then converted by thehinge to a tilt motion around the Y axis indicated by an arrow 256 (FIG.5D). The motion is measured by a Hall-bar sensor 246. In camera module200, the fourth actuator is positioned such that the force applied is inthe +X-Z or −X+Z direction, (at 45 degrees to both X and Z axes, seebelow “magnetic operation” section). However, in other examples, theorientation of the fourth actuator can be such that the force isdirected at any angle in the X-Z plane, as long as torque is appliedaround the hinge axis 232 (for example the fourth actuator as shown inthe embodiment of FIG. 5A). The actuators and Hall-bars sensors ofcamera module 200 are listed in Table 1.

TABLE 1 Force direction Magnetic Coil long (Coil short Actuator CoilMagnet Hall- poles vertex vertex number element element bar directionsdirection direction) 1^(st) 224a 222a 226a ±X ±Z ±Y 2^(nd) 224b 222b226b ±X ±Y ±Z 3^(rd) 224c 222c 226c ±X ±Y ±Z 4^(th) 244  242  246  +X +Z ±Y +X − Z or −X − Z or −X + Z 244  242  246  ±X ±Y ±Z

According to the presently disclosed subject matter, camera module 200further comprises or is otherwise operatively connected to at least onecontroller (e.g. controller 264) configured to control operation of thelens and OPFE actuation sub-assemblies 230 and 260 for generatingmovement to compensate for camera shakes that tilt the camera modulewhen in use, thereby providing OIS. The controller is configured toreceive sensed data indicative of lens and OPFE position and tilt datafrom the gyro and, based on the received data, generate instructions forcausing actuation sub-assemblies 230 and 260 to create movement of thelens module and OPFE that compensates for unintentional tilt of thefolded camera module (and thus provide OIS).

The OPFE tilt compensates for camera tilt about the Y axis. The foldedlens module movement in the Y direction compensates for camera tiltaround the Z axis. The controller receives data on the tilt around Y andtilts the OPFE about Y axis accordingly.

The controller receives data on the tilt around Z and moves the lensmodule in the Y direction accordingly. There may be undesired tilt ofthe lens module about the X axis. As explained further below, in someexamples, the controller can be configured to receive data indicative ofsuch undesired tilt and to provide commands to actuation sub-assemblies230 and 260 for creating tilt power to tilt in an opposite direction tothe undesired tilt.

FIG. 6 shows various views of another embodiment of an OPFE actuationsub-assembly, numbered 290, in which the OPFE is in the form of a prism308 with a reflecting surface 310, according to an example of thepresently disclosed subject matter: (a) isometric view, (b) externalside view, (c) internal side view and (d) bottom isometric view.

OPFE actuation sub-assembly 290 comprises a hanging structure thatincludes four flexible hanging members 292 a-d that hang prism 308 overa base 320. Flexible hanging members 292 a-d are similar to flexiblehanging members 216 a-d, except that instead of being parallel, they aretilted. They are therefore referred to as “tilted hanging members”.Tilted hanging members 292 a-d are fixedly mounted on base 320 at onerespective member end and attached to the prism at another member endthrough hinge points 298 a and 298 b and through side panels 296 a and296 b. In particular, tilted hanging members 292 a and 292 b areattached through hinge point 298 a to side panel 296 a and tiltedhanging members 292 c and 292 d are attached through hinge point 298 bto side panel 296 b. The side panels are fixedly coupled to oppositesides of the prism. Tilted hanging members 292 a-d allow tilting ofprism 308 around a (virtual) hinge axis 294, which is parallel to, oralong the Y axis. Actuation sub-assembly 290 further includes a “fifth”actuator that includes a magnet 344 rigidly coupled to prism 308 and acoil 346 rigidly coupled to base 320. This actuator serves in a similarcapacity as the fourth actuator comprising magnet 244 and coil 246.

In operation, a Lorentz force may be applied between coil 344 and magnet346 to move magnet 346 either to the left (arrow 352) or to the right(arrow 354). This force (and magnet movement) is then converted by thetilted hanging members to a tilt (“pendulum”) motion around axis 294.The tilt may be typically ±1° from a zero (rest) position of the prism.The motion is measured by a Hall-bar (not shown) as explained above.Such an embodiment allows increase in the Hall-bar sensitivity to tiltactuation, by increasing the relative motion between magnet 244 and theHall-bar.

Optical Operation of the Actuator Elements

In compact cameras, focusing and in particular auto-focusing (AF) isperformed by shifting the entire lens module with respect to the cameraimage sensor, such that the following equation is fulfilled:

$\frac{1}{f} = {\frac{1}{u} + \frac{1}{v}}$where “f” is the focal length, “u” is the distance between the objectand the lens and “v” is the distance between the lens and the imagesensor. In camera module 200, focusing (and auto-focusing) may be doneby shifting lens module 204 along the Z axis.

As disclosed herein, OIS is configured to compensate for camera shakesthat shift the camera module in six degrees of freedom (X-Y-Z, roll, yawand pitch). However, as mentioned above, the linear motion in X-Y-Znegligibly affects the image quality and does not have to be compensatedfor. Yaw motion of the camera module (tilt around the Z axis in cameramodule 200) results in image motion along the Y axis on the imagesensor. Yaw motion can then be compensated in camera module 200 by ashift of the lens module 204 along the Y axis. Pitch motion of thecamera module (tilt around the Y axis in camera module 200) will resultin image motion along the X axis on the sensor. Pitch motion can then becompensated in camera module 200 by a tilt of prism 206 around the Yaxis.

Magnetic Operation of the Actuator Elements

Operation of each of the four actuators will now be referred to, bydescribing in detail, and as an example of operation of the firstactuator. Operation of the second, third, fourth and fifth actuators issimilar. FIG. 7 shows elements of the first actuator, i.e. coil 224 aand magnet 222 a, with the associated Hall-bar 226 a. Coil 224 a canhave for example a disco-rectangle (stadium) shape, such that it has onelong vertex 710 and one short vertex 712. According to one example, coil224 a can be made from a copper wire coated by a thin plastic layer(coating) having inner/outer diameters, respectively in the range of40-60 μm, with several tens of turns per coil, such that the totalresistance is typically in the order of 10-30 ohms per coil. Magnet 222a can be for example a permanent magnet, made from a neodymium alloy(e.g. Nd₂Fe₁₄B) or a samarium-cobalt alloy (e.g. SmCo₅). Magnet 222 acan be fabricated (e.g. sintered) such that it changes the magneticpoles' direction: on the left side the north magnetic pole faces thenegative X direction, while on the right side the north-pole faces thepositive X direction. Such “pole changing” magnets are known in the art,and described for example in PCT patent application WO2014/100516A1.

FIG. 8 and FIG. 9A show the first actuator along a cut A-A shown in FIG.7 in isometric and side views respectively. Coil 224 a is shown to havea 60 μm diameter and 48 coil turns. In FIG. 9A, a dot “.” mark indicatescurrent exiting the page plane toward the reader (positive Z direction)and an “x” mark indicates current in the negative Z direction. Themagnetic poles of magnet 222 a are indicated, as is the position ofHall-bar 226 a.

FIG. 9B shows a magnetic simulation along the same cut A-A, where thearrows show the magnetic field direction. The Lorentz force is known tobe equal to:F=I∫dl×Bwhere I is the current in the coil, B is the magnetic field, and d{rightarrow over (l)} is a wire element. Thus, it can be seen that for theindicated current/magnet state, a force which is mostly in the negativeY direction is applied by the magnet on the coil. According to Newton'sthird law, an equal and negative force, mostly in the positive Ydirection, is applied by the coil on the magnet.

In the embodiment presented here, the Hall-bar is located in the vacantarea in the middle of coil 224 a. In other embodiments, the Hall-bar maybe located in another position (e.g. next to the coil), as long as itmagnetically coupled to the corresponding magnet element.

Four Wire-Springs Mechanical Structure

A mechanical structure comprising four round wires can be used forin-plane motion in OIS mechanisms, see e.g. Applicant's published PCTpatent application WO2015/060056, the description and figures of whichare incorporated herein by reference in their entirety. Table 2 belowlists examples of first mode of motion in all six degrees of freedom forwires with diameter in the range of 50-100 μm made for example frommetal (e.g. stainless-steel alloy) and carrying a dual-axis actuationassembly with a total mass of 0.5-1 gram.

TABLE 2 Motion mode Spring constant range Frequency range X ~250000 N/m~300-4000 Hz Y 40-60 N/m 30-60 Hz Z 40-60 N/m 30-60 Hz Tilt around X~0.001 N*m/rad ~60-100 Hz Tilt around Y ~5 N*m/rad ~500-6000 Hz Tiltaround Z ~1.25 N*m/rad ~300-4000 Hz

The typical frequency range for motion in three modes, the Y mode, the Zmode and the “tilt around X” mode is much lower than for the other threemodes. This means that physically, motion in X mode, “tilt around Y”mode and “tilt around Z” mode are much stiffer and unlikely to occurunder low forces like those that exist in the system (on the order of0.01N).

As explained above, motion along the Y axis allows OIS performance,while motion along the Z axis allows AF performance. In known singleaperture camera modules (for example as described in PCT/IB2014/062181),a tilt motion around the X-axis (in the embodiments shown here an axisparallel to the first optical axis) will not influence the image, sincelens modules are axis-symmetric around this axis. In the embodiments offolded-lens cameras disclosed herein the X axis lies in the planecontaining the first and second optical paths and is perpendicular tothe second optical axis. In the cameras disclosed herein, an X-axis-tiltmay cause distortion or shift the image, and is thus undesired.Therefore, two “undesired X-axis tilt” prevention methods are describedbelow.

A first method to prevent X-axis-tilt is to actively cancel it. Thismethod is described with reference to camera module 200. As explainedabove—operation of the first actuator creates a force on magnet 222 a inthe ±Y direction, while operation of second and third actuators createsa force on magnets 222 b and 222 c in the ±Z direction. However, sincethe forces applied on the magnets are also applied on lens actuationsub-assembly 230, which is a rigid body, translation of the force oneach magnet is also translated to a torque on the mass center of lensactuation sub-assembly 230. Table 3 shows the result of force applied oneach of magnets 222 a-c to the mass center of lens actuator sub-assembly230. Using a combination of the three (first, second and third)actuators can create force in the Z-Y plane and torque around the X axissuch that the desired motion is achieved, namely creation of Y motionfor OIS, creation of Z motion for auto-focus, and removal of anyunwanted X-axis-tilt.

TABLE 3 Result of the force action on the mass center of lens Force onmagnet actuation sub-assembly 230 Magnet Force direction Force Torque(around X axis) 222a +Y +Y Counter clockwise −Y −Y Clockwise 222b +Z +ZClockwise −Z −Z Counter clockwise 222c +Z +Z Counter clockwise −Z −ZClockwise

A second method to prevent X-axis tilt is “passive”, and is based onreducing the torque forces created by the first, second and thirdactuators. This method is demonstrated schematically using the actuatorarrangements shown in FIG. 10 and FIG. 11.

FIG. 10 shows a lens barrel 1014 carrying a lens module 1004 withcomponents of three (first, second and third) actuators similar to theactuators in embodiments above (magnets 1022 a, 1022 b and 1022 clocated just above coils 1024 a, 1024 b and 1024 c, respectively).Actuators including these elements do not produce undesired tilt aroundthe X axis. Note that magnet 1022 b and coil 1024 b are shown here asextending substantially (i.e. having a length dimension along) theentire width of the lens barrel (in the Y direction). This arrangementallows the magnet and coil to be positioned between the lens barrel andthe sensor. This is beneficial, since if even part of the actuator ispositioned below the lens barrel, the total height of the module (in theX direction) increases below a required height, Exemplarily, the lengthof magnet 1022 b and coil 1024 b in the Y direction may be ca. 7-8 mmand the width of magnet 1022 b and coil 1024 b in the Z direction may beca. 2-3 mm. The height of all coils is exemplarily ca. 0.5 mm. Thearrangement of the first, second and third actuators is such that thetorque on mass center of lens actuation sub-assembly is minimal. Thatis, these actuators do not produce undesired tilt around the X axis.Table 4 shows the translation of force on each of magnets 1022 a-c tothe mass center of the lens actuation sub-assembly.

TABLE 4 Result of the force action on the mass center of the Force onmagnet lens actuation sub-assembly Magnet Force direction Force Torque(around X axis) 1022a +Y +Y Negligible −Y −Y Negligible 1022b +Z +ZNegligible −Z −Z Negligible 1022c +Y +Y Negligible −Y −Y Negligible

FIG. 11 shows an arrangement for lens actuation with two actuators,according to an example of the presently disclosed subject matter. Theactuator arrangement uses only two (e.g. first and second) actuators ofthe actuators in FIG. 10. This arrangement is simpler, as it may achievethe same result while removing one actuator from the arrangement of FIG.10.

FIG. 12A shows schematically an isometric view of another folded cameramodule numbered 1100, according to an example of the presently disclosedsubject matter. Note that the X-Y-Z coordinate system is orienteddifferently than in FIGS. 1-11. Folded camera module 1100 comprises animage sensor 1102 having an imaging surface in the X-Y plane, a lensmodule 1104 with an optical axis 1106 defined above as “second opticalaxis” and an OPFE 1108 having a surface plane 1110 tilted to the imagesensor surface, such that light arriving along a first optical path ordirection 1105 is tilted by the OPFE to the second optical axis ordirection 1106.

FIG. 12B shows folded camera module 1100 with the folded lens moduleremoved from its mounting. FIG. 12C shows the folded lens module in (a)a regular isometric view and (b) turned upside down.

In an embodiment, camera module 1100 comprises a lens actuationsub-assembly for moving lens module 1104 for autofocus in the Zdirection. This sub-assembly may include a single actuator with a magnet1122 ab and a coil 1124 b. In other embodiments, camera module 1100 maycomprise a lens actuation sub-assembly for moving lens module 1104 inthe Y-Z plane. However, in contrast with the 3-actuator lens actuationsub-assembly shown in FIGS. 3 and 10, the actuation sub-assembly infolded camera module 1100 comprises four actuators operating on the lensmodule. In other words, an additional “fifth” actuator is added to thefirst, second and third actuators of the lens actuation sub-assembly:here, the first actuator includes a magnet 1122 ab and a coil 1124 a,the second actuator includes magnet 1122 ab and coil 1124 b, the thirdactuator includes a magnet 1122 c and a coil 1124 c. The added (“fifth”)actuator includes magnet 1122 d and a coil 1124 d. The magnet and coilarrangement is similar to that in FIG. 10, in that magnet 1122 b andcoil 1124 b are positioned between the lens module and the image sensor,enabling efficient Z-axis actuation (for autofocus). The actuatorsincluding magnet 1122 ab and coil 1124 a, magnet 1122 ab and coil 1124 band magnet 1122 d and a coil 1124 d may be used actively to preventundesirable tilt around the X-axis. Two Hall-bar sensors 1126 b′ and1126 b″ measure displacement in the Z direction and tilt around the Xaxis. A Hall-bar sensor 1126 c measures displacement in the Y direction.

The long coil dimension in the Y direction provides high efficiency forautofocus action in the Z direction. To illustrate how a coil electricalpower (P_(e)) and mechanical force (F) depend on the coil size, one cananalyze a simple case of a single-turn coil. A coil with a wirecross-section area S is placed on a Y-Z plane and has exemplarily arectangular shape with two sides of length L_(y) parallel to Y and twosides of length L_(Z) parallel to Z. The permanent magnet (ferromagnet)that produces the magnetic field in the coil is designed to maximize theforce between coil and magnet in the Z direction (F_(t)), resulting fromcurrent I flowing in the coil. In this case, F_(Z)=2k₁IL_(y) where k₁ isa constant depending (among others on the magnetic field strength. Thecoil electrical power is P_(e)=2k₂I²S(L_(z)+L_(y)), where k₂ is adifferent constant. Efficient magnetic engines have high F_(z) for lowP_(e). An efficiency factor (E_(f)=F_(z)/P_(e)) can be derived as:E _(f)=((k ₁ ²)*S)/(k ₂ *F _(z))*L _(y)/(1+L _(z) /L _(y))or, by using I=F_(z)/(2k₁L_(y))E _(f)=[((k ₁ ²)*S)/(k ₂ *F _(z))]*L _(y)/(1+L _(z) /L _(y))

From the above it is clear that if L_(y) is increased by a factor of 2(everything else being equal), then E_(f) will increase by a factorgreater than 2. Thus, the longer the coil in the Y direction, thebetter. The positioning of magnet 1122 c between the lens module and theimage sensor advantageously allows to lengthen the magnet in the Ydirection to approximately the lens module carrier width. Exemplarily,coil 1124 c has a long dimension or vertex (typically ca. 7-8 mm) in theY direction and a short dimension or vertex (typically ca. 2-3 mm) inthe Z direction. In general, for single- or multi-turn coils, the longerthe coil in the direction perpendicular to the magnetic force, the moreefficient will be the magnetic engine utilizing this coil.

The positioning of the magnet of the AF actuator between the lens moduleand image sensor may cause light reflections of light arriving along theoptical axis of the lens (Z-axis). Such reflections may affect the imageacquired at the folded camera image sensor. In order to prevent suchreflections, the magnet (i.e. magnet 1122 c) may be a coated with anabsorption and scattering coating (FIG. 12C and FIG. 13), for example anActar Black Velvet coating manufactured by Actar Ltd., Kiryat Gat,Israel. Alternatively or in addition, the magnet can have perturbationsin the shape of waves or other shapes to further scatter reflectedlight. Alternatively, a wavy thin plate structure (“yoke”) 1130 with anabsorption and scattering coating as above may be attached to themagnet.

In summary, some camera embodiments disclosed herein include at leastthe following features:

1. Fully closed loop AF+OIS functionality.

2. Slim design, no height penalty.

3. Low cost design:

-   -   Integrated circuitry for OIS, AF and camera sensors.    -   Moving mass which is completely passive—no need to convey        electricity to moving objects.

While this disclosure has been described in terms of certain embodimentsand generally associated methods, alterations and permutations of theembodiments and methods will be apparent to those skilled in the art.For example, while the incorporation of a folded camera module describedherein in a dual-aperture camera is described in some detail, a foldedcamera module may be incorporated in a multi-aperture camera having morethan two camera modules. For example, while the use of Hall-bars as anexample of position sensors is described in detail, other positionsensors (for example micro-electro-mechanical system (MEMS)-typeposition sensors) may be used for purposes set forth herein. Thedisclosure is to be understood as not limited by the specificembodiments described herein.

It is emphasized that citation or identification of any reference inthis application shall not be construed as an admission that such areference is available or admitted as prior art.

What is claimed is:
 1. A folded camera module, comprising: a) a lensmodule having a lens optical axis; and b) an optical path foldingelement (OPFE) for folding light from a first optical path to a secondoptical path towards an image sensor, the second optical path beingalong the lens optical axis, wherein the lens module is designed to bemoved for auto-focus (AF) along a first direction substantially parallelto the lens optical axis, and wherein the OPFE is designed to be tiltedfor OIS only around an OPFE tilt axis that is parallel to a seconddirection to compensate only for tilt of the folded camera module aroundthe second direction, wherein the second direction is substantiallyorthogonal to both the first and second optical paths.
 2. The foldedcamera module of claim 1, further comprising: c) a lens actuationsub-assembly configured to actuate the lens module movement in the firstdirection; and d) an OPFE actuation sub-assembly configured to tilt theOPFE around the OPFE tilt axis.
 3. The folded camera module of claim 2,further comprising one or more position sensors that enable measurementof a position of the lens module and measurement of OPFE tilt.
 4. Thefolded camera module of claim 3, further comprising an actuationcontroller configured to receive a data input indicative of the foldedcamera tilt and a data input from the one or more position sensors andto generate, in response to the data inputs, movement instructions andtilt instructions to, respectively, the lens and OPFE actuationsub-assemblies.
 5. The folded camera module of claim 2, wherein each ofthe lens actuation sub-assembly and the OPFE, actuation sub-assemblyincludes a plurality of flexible hanging members.
 6. The folded cameramodule of claim 5, wherein the flexible hanging members of the lensactuation sub-assembly are parallel to each other.
 7. The folded cameramodule of claim 5, wherein the flexible hanging members of the OPFEactuation sub-assembly are tilted.
 8. The folded camera module of claim1, wherein the OPFE tilt axis is a virtual axis.
 9. The folded cameramodule of claim 2, wherein the OPFE actuation sub-assembly includes atleast one coil-magnet pair for actuating the OPFE tilt.
 10. The foldedcamera module of claim 9, wherein at least one of the coil-magnet pairis positioned below the OPFE.
 11. The folded camera module of claim 1,wherein the OPFE includes a prism or a mirror.
 12. The folded cameramodule of claim 2, wherein the lens actuation sub-assembly includes aplurality of coil-magnet pairs for actuating the lens module movement.13. The folded camera module of claim 12, wherein the plurality ofcoil-magnet pairs includes two coil-magnet pairs.
 14. The folded cameramodule of claim 12, wherein at least one of the plurality of coil-magnetpairs is positioned between the lens module and the image sensor.
 15. Amethod of providing optical image stabilization (OIS) and auto-focus(AF) in a folded camera module, the folded camera module comprising alens module having a lens optical axis and an optical path foldingelement (OPFE) for folding light from a first optical path to a secondoptical path towards an image sensor, the second optical path beingalong the lens optical axis, the method comprising: a) moving the lensmodule for AF along a first direction substantially parallel to the lensoptical axis; and b) tilting the OPFE for OIS only around an OPFE, tiltaxis parallel to a second direction to compensate only for tilt of thefolded camera module around the second direction, wherein the seconddirection is substantially orthogonal to both the first and secondoptical paths.
 16. The method of claim 15, further comprising: c)operating a lens actuation sub-assembly configured to actuate the lensmodule movement along the first direction; and d) operating an OPFEactuation sub-assembly configured to actuate the tilt of the OPFE aroundthe OPFE tilt axis.
 17. The method of claim 16, wherein each of the lensactuation and OPFE actuation sub-assemblies includes a plurality offlexible hanging members, the method further comprising tilting theflexible hanging members of the OPFE actuation sub-assembly.
 18. Themethod of claim 15, wherein the tilting the OPFE is around a virtualaxis.